it's not a fine, it's a tax -- a tax for everybody over a certain income level, to help pay for healthcare for everyone else. Sure, they wave the tax if you already have health insurance, or if you're poor. That's nice of them. But it's just a tax.
Of course you go to jail if you refuse to pay taxes. Duh. Nobody is sending you to jail because you opt not to get insurance. If you don't want insurance, don't get it. You might have to pay a tax though. You've got to pay your way, one way or another.
This isn't rocket science.